Has anybody ever tried to hypnotize you at work without your knowledge? Don't laugh. It happened to me and the rest of the employees at my work. My boss gathered us all together for a pep talk to motivate us to work harder.
He told us all to close our eyes, and just listen. Then he spoke in a soothing voice about visions of the paradise work would be soon, the kind of facilities we would work in, the happiness we would all share, etc.
Of course, nobody's work improved after that. But what did he care? He is into all kinds of things, theories about "visualization" (the idea that if you visualize something, it will magically come true), Neuro-linguistic Programming, and something called "Ericksonian Hypnosis." These areas of bullshit are nothing more than new age nonsense that is sold by rip-off artists for stupid people (like my boss at the time).
Despite the silliness of that, though, there is the ethical question of trying to manipulate people this way. Sure, it's ineffective, and you might therefore think it is harmless. But consider what else might be employed by jerks who employ such methods in the first place. The same boss once slandered me, accusing me of "gloating" over a monumental disaster he had created, this accusation coming out of nowhere. When I asked him where he came up with that idea, he said "it's your body language." How do you defend yourself against that type of baseless slander? It's so silly you can't defend against it, and I think that's why he made the accusation. (After that, I wanted to show some unmistakable body language to him, but I didn't.) So, people, the answer is no, it's not harmless when you have somebody in charge who is willing to engage in unethical and abusive workplace behavior.